Electrical relay.



S. G. BROWN.

ELECTRICAL RELAY.

APPLICATION FILED D110. 2;, 1912.

Patented Feb. 16, 1915.

2 SHEETS-SHEET l.

S. G. BROWN.

, ELECTRICAL RELAY.

APPLIOATION FILED D30. 23, 1912.

Patented Feb. 16, 1915.

2 SHEETS-SHEET 2.

' SIDNEY enoncn enown, or- LONDON, ENGLAND.

ELECTRICAL RELAY.

Specification of Letters Patent.

Patented rep. 1c,-1a1a.

Continuation in part of application Serial No. 669,151, filed January 3, 1912. This application filed December 2a, 1912. Serial No. 738,339.

To all whom it may concern Be it known that I, SIDNEY GEORGE BRowN, a subject of the King of Great Britain, residing at 4: Great Winchester street, in the ity and county of London, England, have invented certain new and useful Improvements'Relatingl'to Electrical Relays, of

which the following is a specification.

This invention relates to electrical relays, and has particular reference to relays for use in wireless telegraphy or in transmission over long tele hone lines. The currents for operating a telephone relay are frequently so weak or exhausted that the relay fails to respond properly unless particular care has been taken in its construction. The typeof microphone relay disclosed in the specification of my prior United States Patby experiment, however, that a reduction in size of the cell containing the granules accompanied by corresponding changes in 00- operating parts of the relay enables an eiii: cient granular form of relay to be obtained. The type of relay I use is one in which a vibratory member such as a metal reed serves as armature to an electromagnet through which the weak line currents pass, and carries one of two contact pieces between which the granules are located, these contact pieces and the granules forming a granular microphone. I

In order to obtain the highest eiiiciency of transmission of the vibratory movements of the armature from the latter to the micro phone it is necessary for the contact piece carried by the armature to be small in terminal area. It is on this account that granular microphones of customary size cannot be used efficiently in telephone relays. From the mechanical point of view the microphone and hence also the column of granules should be small in diameter or cross section. From the electrical point of view, however, the value of the maximum resistance that the granules should otter has a limit.

According to the present invention the relay ofthe type hereinbet'ore specified comprises a granular microphone so small in diameter or cross section that the dead weight of the granules only just sutlices to afford the necessary degree of conductivity for the local or sending-on current, such diameter being of the order of .3 of an inch.

In addition to the line windings upon the usual polarized electromagnet of the relay, I findit advantageous to provide another set of windings, these forming part of the local circuit by being connected in series with the .microphone. These local current windings are especially useful if the relay is used at an intermediate station as hereinafter explained. In addition to the electromagnet windings through which the line currents pass, and the windings through which the local current passes, the electromagnet may also have wound upon it counteracting windings that are brought into action only if the attracting force exerted upon the armature bv the other windings becomes excessive, the effect of these counteracting windings then being to neutralize this attracting force. The provision of such counteracting means is especially advantageous with relays of the delicate order described in order to prevent their delicacy or sensitiveness from becoming unduly disturbed.

The microphone itself is preferably formed by securing a flexible diaphragm over the mouth of a hollowed-out cylinder about .35 of an inch in diameter internally, a carbon-faced disk being attached centrally to the diaphragm to serve as the movable contact piece of the microphone and the hollow space within the cylinder serving as a chamber for the granular microphonic ma terial, preferably carbon; the depth of this chamber should be about .06 of an inch. The carbon-faced disk and the diaphragm are secured to the free end of a reed serving as armature to the electromagnet of the relay. The hollowed-out cylinder serving as the back contact piece of the microphone may be provided with a stem by which it can be rigidly fixed in position, or the said back contact piece may be carried on one end of a spring-controlled balanced arm; alterna tively the back contact piece can be without am special support and derive its support from the movable contact piece, provided I the said back contact piece has a certain degree of inertia as hereinafter-explained.

in order that the invention may be clearly understood and readily carried into effect the same will now be described more fully with reference to the accompanying drawings in which Figure 1 is a diagrammatic plan of one form of my improved relay and its connections to the line and to a local circuit.- Fig. 2 is a diagram of electrical connections in the local circuit including the connections for the counteracting coils. Fig. 3 is an enlarged vertical section of a preferred construction of the microphone. Fig. 4: is an elevation and Fig. 5 a plan of a complete instrument. Fig. 6 is an incomplete view of a modified arrangement of the microphone hereinafter described.

Referring first more particularly to Figs. 1 and 2, A A are the line Wires leading to and from line current windings A. and B B are the wires leading to and from local current windings B. C is a polarized electromagnet. The windings B are wound around the upright limbs and the counteracting windings hereinbefore referred to, and shown in'Fig. 2 by the reference letters B, are also wound upon these limbs. The limbs may be inclosed' in copper sheathing (not shown) in order that eddy currents set up in the sheathing may tend to neutralize the self induction of the superposed windings. The windings are wound upon laminated pole pieces C secured horizontally by brass screws to the poles oi the electromagnet C. The free ends of the pole pieces C are close together and are situated behind the armature D. E is the granular microphone, this being included in the local circuit which includes also the windings B, a switch 13*, source of electric current B indicator B, and transformer winding B The other transformer winding B is included in the actual circuit of a telephone receiver B. The reed Ditself may take the form of a steel reed-the free end of which may be of steel or of soft iron. An intermediate part of the reed is preferably cut away as at D in order to impart the requisite resiliency to it.

In Fig. 2 the reed is shown as being held against a rounded bridge piece D by two screws D ,-one on each side of the bridge piece, the lower one being a'thumb screw ticularly to the constructional form of the microphone as shown in Fig. 3, it is seen that the microphone comprises the hollowedout and flanged brass cylinder F, about .35 of an inch in internal diameter, providing a. cell or chamber containing the carbon contact piece F and having clamped to it the mica diaphragm F The central region of this diaphragm is clamped to the front carbon-faced brass contact piece F about .02 of an inch thick and .3 of an inch in diameter around which is a layer of felt F about .02 of an inch thick. The space between the two contact pieces F and F 3 is occupied by carbon granules and is about .06 of an inch wide. For increased delicacv the internal diameter of the cylinder may be as small as .25 and the front contact piece .2 of an inch in diameter, the other dimensions being as before. The layer of felt F prevents the granules from working their way behind the contact piece F without impairing the flexibility of the diaphragm; this layer of felt also serves to. prevent the diaphragm from vibrating too freely, and therefore insures clear speech. The sides of the cell or chamber may be lined with felt also. By attaching the elastically mounted front contact piece F to the upper portion of the armature D, the motion of the armature is controlled and its free period, which should be of the order of one thousand complete periods per second, is effectively damped, Producing great clearness of speech. As regards the damping of the armature D and the effect produced by. such damping upon the clearness of speech,.I have found that if the microphone, instead of being on a level with the pole pieces Chis raised, that is to say, if the attachment of the armature to the microphone is nearer the free end of the armature than is shown in Fig. 4, the extra damping thus produced on the armature improves the clearness of speech. Alternatively a small pad of rubber might be provided to press lightly upon the armature and thereby, of course, damp its movements. By arranging the microphone cell with so small a diameter, and such small depth, the quantity of carbon granules necessary to fill it is very small, resulting in great sensitiveness to pressure and nearly complete freedom from packing, a combination of qualities that is essential to the successful working of this kind of relay.

The cylinder F is provided with a central rearward projection F which fits into a socket in a bracket F When first adjusting the relay, the attachment of the rearward projection F in its socket is slackened to allow the cylinder and hence also the whole microphone to take up an unconstrained position relatively to the reed D so that the granules are not under any initial positively applied pressure; the projection F is then tightened in its socket. The regulating windings B, when used in this form of relay,-namely one in which the dead weight of the granules in the microphone is sufficient to afford the requisite conductivity, have a beneficial effect by their reacting effect on the control of the microphone. This client is especially beneficial if this form of relay is used at an intermediate station instead of at the end of a long line, because the local regulating windings B have the effect of preventing the excessive drop in strength which the steady current traversing the microphone might otherwise experience by the arrival at the intermediate station of comparatively strong line currents. It is known that the steadycurrent normally traversing a microphone experiences a drop in strength directly the micro phone becomes operative; the more vigorously the microphone is actuated the greater is this drop in current; hence it will be understood that, since in the above mentioned form and use of the relay, the microphone is exceedingly sensitive, (being without initial pressure), and is assumed to be situated at an intermediate station (where of course the arriving currents may be stillv comparatively strong), the movable contact piece of the microphone might be actuated so much as to cause a large drop in the steady current traversing the microphone; a large drop in this current is undesirable, since it is the effect ofthe steady current that produces the increase of power for the remainder of the line extending to a distant instrument. The regulating windings B, however, which are in series with the microphone, cause a counteracting effect to be exerted upon the reed carrying the movable contact of the microphone and thus prevent the excessive drop referred to.

Alternatively to the rigid back contact piece, the said contact piece may possess a certain amount of resiliency. One such arrangement is shown in Fig. 6, where it is seen that the contact piece E is carried on a balanced arm pivoted at e and held stationary by a spring 6. According to a further modification the back contact piece may be neither rigidly fixed nor adj u'stably mounted but may be carried bodily by the reed D, as would result for example by removing the bracket F from Fig. 4; then, if the back contact piece or a member attached to it is suiiiciently inert, the microphone will respond as a whole to any relatively slow movei'nents of the reed but not to vibratory movements corresponding to currents of telephonic frequency. It will be understood that the maximum frequency or pitch of the vibratory movements, on the part of the movable front contact piece, to which the rear contact piece, or backing as it may be termed. responds will depend upon the inertia of the backing and hence also upon its weight. A backing that is comparatively light will vibrate with the movable contact piece to all but very high frequency vibrations and the relay will therefore be active only to incoming current variations of correspondingly high frequency, whereas with a backing of greater weight the greater in-' ertia will cause the relay to become active to current variations of lower frequency. Hence by suitably choosing or regulating the inertia of the backing the pit-oh to which the relay most readily responds'm'ay be de-' termined. In order that the backing may possess the requisite inertia it may be made with a thick back or base, but it is preferable to attach a weight, which weight is adapted to be removed and replaced by a diiferent weight if a different inertia is required. The inertia effect of the backing may be produced otherwise than by making it heavy.

It will be seen from Figs. 2, a and 5, that the reed D is provided at its free end with a tongue D reaching between 'two stops D and D. Under normal conditions of work. ing the amplitude of vibration of the reed is tongue D and the stops D, D, but when 'the attraction of the electromagnet pole pieces C becomes excessive this contact takes place; the effect is to complete the circuit of one or other of the counteracting windings B", B", which, together with a resistance D are included in circuits adapted to derive current from the battery B as clearly shown in Fig. 2. The windings B",

B", are wound co-ax1al1y with the windings B, B, and are arranged to reduce or increase respectively the strength of the magnetic circuit, thus preventing the reed D side sources and passing through the instrument. 1

In the particular form of the relay as shown in Figs. 4 and 5 the polarized steel electromagnet C is arranged vertically, with the regulating coils B and the counteracting coils B" wound around its limbs and the line windings A wound upon horizontal pole pieces (.3 The circuits of the counteracting coils l3 are controlled by the tongue D and the stops D and D (broken away in Fig. 5), the said stops being carried upon a bracket 1) (Fig. 5) secured to but insulated from the main structure. of a relay having a microphone about threetenths of an inch in diameter and no initially applied pressure the battery voltage and the resistance of the telephone or primary of the transformer may be about six volts and from 25 to 30ohms respectively, in which case the current normally traversing the microphone would be about 60 or milliamperes while with a microphone about one fifth of an inch in diameter the current would be about 30 milliamperes.

In the foregoing description it may be assumed that the electromagnet of the relay is not sufiicient to produce contact between the In the case a polarized electromagnet since even if it is not initially polarized it is virtuall polarized when the local circuit is c osed, owing to the presence of the local current windings.

What I claim and desire to secure by Letters Patent of the United States is 1. A telephone relay comprising line current windings, a vibratory member responmicrophonic material, two oppositely placed contact pieces about .3 of an inch in effective diameter and separated a suflicient distance apart to obviate initial compression of the granular material, said contact.pieces forming part of the local circuit of the relay and one of them moving with the. vibratory member, a wall retaining the said granular material between the contact pieces, the dead Weight of the inclosed granules suflicing Without initially applied pressure to afiord the requisite initial conductivity for the local current from one contact piece to the other, and means for manually adjusting the initial distance apart of the contact pieces.

2. A telephone relay comprising line current windings, a vibratory member responsive to the line current variations, regulating windings forming part of the local circuit of the relay, granular microphonic material, two oppositely placed contact pieces about .3 of an inch in effective diameter and separated a sufiicient distance apart to obviate initial compression of the granular material, said contact pieces forming part of the local circuit of the relay and one of them moving with the vibratory member, and a wall retaining the said granular material between the contact pieces, the dead weight of the inclosed granules sutlicing without initially applied pressure to afford the requisite initial conductivity for the local current from one contact piece to the other, and means for manually adjusting the initial .distance apart of the contact pieces.

3. A telephone relay, comprising line current windings, a vibratory member responsive to the line current variations, granular microphonic material, a contact piece about .3 of an inch in effective diameter on the vimicrophonic material, av contact piece about sive to the line current variations, granular- .2 to .3 of an inch in effective diameter on the vibratory member, a second but stationary contact piece .25 to .35 of an inch in effective diameter opposite the first mentioned contact piece but spaced therefrom about .06 of an inch, said contact pieces forming part of the local circuit of the relay, a cylindrical wall ,25 to .35 of an inch in internal diameter integral with the stationary contact piece and extending toward the other contact piece and retaining between the contact pieces the granular material in an initially uncompressed condition, a flexible diaphragm over the open end of the said wall, means whereby the last metioned contact piece, the diaphragm, and the vibratory'member, are held together, means for manual adjustment of the vibratory member.

5. A telephone relay comprising a granular microphone consisting of front and back contact pieces of the order of .3 of an inch in diameter, and initially uncompressed granules inclosed between them, a resilient reed responsive to the line currents and carrying one of the microphone contact pieces, a tongue on said reed, stops for cooperation With said tongue, and counteracting coils on the relay connected to the stops; whereby excessive vibration of the reed causes the counteracting coils to become momentarily active.

6. A telephone relay comprising an electromagnet, a granular microphone consisting of front and back contact pieces of the order of .3 of an inch in diameter and initially uncompressed granules inclosed between them, a resilient reed responsive to the lines current passing through the wind ing of the relay electromagnet, means whereby one contact piece of the microphone exactly follows the movement of the reed, means whereby the remainder of the microphone is supported by the reed without participating in vibrations of telephonic frequency of said reed, and means for manual adjustment of the reed.

7. A telephone relay, comprising a polarized electromagnet, a resilient reed serving as electromagnet armature, a contact piece carried by said armature, an oppositely situated stationary contact piece, initially uncompressed granular material confined between said contact pieces, a laterally inextensible cylindrical wall of about .2 to .3 of an inch in diameter confining the granular material, electromagnet windings forming part of the line circuit, electromagnet windings forming part of the local circuit and connected in series with the aforesaid contact pieces, meansfor adjusting the position of the reed relatively to the electromagnet, and means for limiting the extent of vibratory movement of the reed.

8. A telephone relay, comprising a. polarized electromagnet, an electrnmagnet armature, an initially uncompressed granular microphone about .2 to .3 of an inch in diameter having one contact piece carried by said armature, electromagnet 'windings forming part of the line circuit, electromagnet windings forming part of the local circuit and connected in series with the microphone, electromagnet windings acting to counteract the effect upon the armature of the other windings, and mean cooperating with the armature for controlling the circuit of the counteracting windings.

9. A telephone relay comprising arpolarized electromagnet with vertically directed poles, local current windings thereon, laminated pole pieces secured'horizontally to the poles of the electromagnet, line current windings upon the pole pieces, a resilient reed serving as electromagnet armature, 20 means for manually adjusting the position of the reed relatively to the electromagnet, two contact pieces .2 to .3'0f an inch in effective diameter forming part of the local windings circuit and spaced apart upon a 25 horizontal axis, and initially uncompressed granular material inclosed between them, one contact piece being on the aforesaid reed and the other secured to a stationary part of the relay.

In testimony whereof I affix my signature in presence of two Witnesses. SIDNEY GEORGE BRUWN.

Witnesses:

'I. SELBY IVARDLE, W'. I. SKERTEN. 

